Standardize running location for scripts

Certain scripts, like `jsonld_approach/simssadb/jsonld/generate_jsonld.py` are written with the expectation that the program will be run from the directory that contains the script, while other scripts, like `code/musicbrainz/fetch.py` is written with the expectation that it will be run from the repository root. Furthermore, some scripts, like `code/musicbranz/untar.py` expect arguments to specify input and output directories.

This is something that should be standardized across the repository.